Each tree that Richard Campbell walks past in the Florida orchard where he works reminds him of a person, a place, and a story. One of Campbell’s favorite botanical biographies here is that of the Blas avocado, a large green-skinned fruit with flesh as runny as warm butter. He first found the tree about a decade ago in a village called San Mateo in the coastal lowlands of Costa Rica. According to local lore, the tree—a gnarly old giant with smooth skin and olive-green, half-moon leaves—had grown from an avocado pit discarded more than a century before. The tree’s fruit had garnered such regional fame that some people would travel nearly 100 miles during harvest time to collect piles of it in oxcarts.
Campbell located the owner of the tree and got his permission to remove several branch tips for grafting. Today, two clones of the original grow in the Fairchild Tropical Botanic Garden in Coral Gables, Fla., where Campbell and several other fruit collectors have established a vast collection of tropical tree fruits, including mangos, jackfruits, mamey sapotes, and durians. There are some 200 varieties of avocados alone, most of them collected by Campbell and his frequent collection partner, Noris Ledesma, between 2002 and 2008 on a series of expeditions to Central America and the Caribbean. This region, bounded by Hispaniola, Panama, and southern Mexico, is the place of wild origin of the West Indian avocado. This subspecies of Persea americana, or the common avocado, is distinguished by its fruit’s smooth green skin, low oil content, sweet and juicy flesh, and large size—usually more than a pound in weight. For many people in Latin America, this fruit is a dietary staple, often used in smoothies, ice cream, avocado mousse, and even juice. (By contrast, the popular Hass avocado—a hybrid of the Mexican and Guatemalan subspecies—has thick, oily meat, well suited for guacamole.)
Florida farmers have grown West Indian avocados for years, though only a few varieties. Campbell and Ledesma believe that thousands more exist in the coastal areas south of the Bahamas. Here grow native avocado varieties that occur nowhere else in the world, making them especially valuable to geneticists seeking to preserve and study rare plants. Campbell and Ledesma’s goal is to collect as many of these undiscovered avocado types as possible and preserve them in the Fairchild collection. This ambition is not merely the product of aesthetic appreciation of the fruit. In truth, thanks to development, deforestation, and climate change, avocado breeds are disappearing more quickly than Campbell and Ledesma can collect them, and many types could disappear before they are even discovered.
Fruit collectors have been embarking on exotic tree-hunting safaris for centuries. The first leg of the famously doomed 1787 voyage of Lt. William Bligh on the soon-to-be-mutinied HMS Bounty was, in fact, a mission to collect breadfruit saplings in Tahiti. Bligh’s assignment was to transport the young trees from the Pacific to the Caribbean and thereby introduce a new source of food to the islands’ slave camps. A century later, the U.S. Department of Agriculture sent several explorers to Turkey, Greece, Italy, and North Africa in search of desirable fig varieties, with the hope (ultimately successful) of launching a profitable industry in the similar climes of California. At about the same time, David Fairchild, for whom the Fairchild Garden is named, was conducting his own exotic plant exploration for the United States government. Fairchild ultimately helped introduce pistachios, nectarines, Chinese soy beans, and mangos to Americans.
Today, scientists from many nations continue the hunt for new or exotic plants. Carrying GPS locators and traveling in jeeps, they pursue wild seedlings or unknown cultivated varieties throughout Asia, equatorial Africa, and Latin America and bring their finds back for propagation in botanical collections. The Fairchild Garden is just one facility of its sort. A vast apple collection in upstate New York, managed jointly by Cornell University and the USDA, includes some 8,000 accessions. Near Sacramento, Calif., the USDA and UC-Davis co-manage an orchard containing thousands of grape, walnut, almond, kiwi, persimmon, and fig varieties, among others. And in Corvallis, Ore., another government-university collection includes blackberries, raspberries, hazelnuts, and hops. The United States isn’t the only player in this game, either: The Greek government, for example, keeps a huge assortment of olive trees near Kalamata.
These collections, and many others like them, are genetic libraries that preserve natural diversity within species and offer farmers new varieties to grow and sell. (Even home gardeners may access many of the plants grown at these facilities.) Perhaps more importantly, varietal plant collections provide genetic building blocks for the use of fruit breeders, many of whom work with the USDA to develop tastier and higher-yielding fruits. Other breeders focus on creating disease-resistant or drought-tolerant varieties, both increasingly important as climate change begins to pose new challenges for farmers.
Plant-collecting outings are usually focused on known regions of indigenous abundance. For example, a major hotspot of apple and walnut diversity lies in Asia’s Caspian and Aral basins, where many thousands of wild and cultivated varieties grow. Explorers targeting grapes have traveled in the Republic of Georgia, while those seeking bananas have looked to Southeast Asia and Central Africa. Typically the most valuable material is found in wild forests and other wilderness regions, though populated areas are often the best places to look for high-quality fruits, since local people have usually already found (or bred) their region’s most appealing varieties.
While jetlagged collectors can make valuable finds by driving rental cars through towns with one eye peering over fences and into backyards, an even better place to begin a fruit-hunting trip is a village’s farmers market or bazaar. Here, among the many piles and crates of local fruits and vegetables, may dwell treasures—fruits harvested from backyard trees that aren’t known outside the region. When hunting for new avocados, Campbell and Ledesma browse such outdoor markets in search of fruits with outstanding physical features. “We basically want trees that have unusual fruit—whether long, big, purple-skinned, without a seed, whatever,” Campbell explains.
If the local market lacks interesting fruits, Campbell and Ledesma may work a trick that has many times drawn great avocados out from hiding: They drive slowly through the dirt streets of a village and, using a bullhorn, invite all the locals to bring their homegrown avocados to a weekend fruit competition, at which the best avocado will win its owner a new bicycle, previously purchased at a local shop on the expedition’s expense account. A small crowd of locals, Campbell says, is almost sure to gather at the appointed place with samples of their backyard fruits.